A nitride semiconductor has characteristics such as high saturation electron velocity and a wide band gap. Accordingly, various studies are being made on the application of a nitride semiconductor to a high withstand voltage and high output semiconductor device utilizing the characteristics. For example, GaN-based high electron mobility transistors (HEMT) have recently been used as power devices.
The power-added efficiency and output of a transistor can be improved by reducing its drain resistance, and the drain resistance can be reduced by shortening the distance between a gate electrode and a drain electrode.
The shortening of the distance between the gate electrode and the drain electrode, however, leads to an increase of a gate leakage current to lower reliability.
Patent Document 1: Japanese Laid-open Patent Publication No. 2006-128646
Patent Document 2: Japanese Laid-Open Patent Publication No. 2009-26838
Patent Document 3: Japanese Laid-Open Patent Publication No. 2015-12037